Turbofan flow path trenches

ABSTRACT

An integrally bladed disk includes a rotor disk and circumferentially spaced first and second blades. The rotor disk has a rim the periphery of which forms a flow surface. The first and second blades extend integrally outward from the rim. The rim defines a trench in the flow surface between the first and second blades aft of a leading edge of the rim. The trench extends axially forward and rearward of a leading edge of the first blade.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a continuation of U.S. patent application Ser. No.12/560,710, filed Sep. 16, 2009.

BACKGROUND

The present invention relates to gas turbine engines, and moreparticularly, to integrally bladed disks in gas turbine engines.

The fan, turbine and compressor sections of gas turbine engines includeone or more circumferentially extending rows or stages of airfoils,commonly called rotor blades, which are axially spaced between rows orstages of fixed airfoils (stator vanes). The rotor blades are connectedto and extend radially outwardly from a rotor disk. During operation thecentrifugal loads generated by the rotational action of the rotor bladesmust be carried by the rotor disk within acceptable stress limits.

Conventional rotor blades are carried in the rotor disk by a dovetail orfir tree root which slides into and interlocks with a correspondingdovetail slot in the perimeter of the rotor disk. However, as the numberof rotor blades around the perimeter of the disk increases, insufficientmaterial is available for supporting the plurality of rotor bladeswithin acceptable stress limits. Accordingly, integrally bladed diskshave been developed and are commercially used. Integrally bladed disksdo not utilize the interlocked dovetail design but instead areintegrally joined to the rotor blades as a single-piece, unitaryassembly by milling, forging, casting or other known manufacturingoperations.

Integrally bladed disks can be used to increase aerodynamic efficiencyof the gas turbine engine while reducing the stresses associated withsupporting the rotor blades. One of the stresses associated withsupporting the rotor blades is a hoop stress. The hoop stress is definedas a load measured in the direction of the circumference of a rotatingbody, the load being created by thermal gradients and centrifugal forcesacting in a radial direct outwardly from the axis of rotation of thebody. The hoop stress is particularly acute where the gas turbine engineutilizes integrally blades disks. Integrally bladed disks have beenknown to develop fractures along their perimeter during operation due tothe hoop stress and principle stresses. These fractures necessitatereplacement of the integrally bladed disks to avoid a catastrophicfailure.

SUMMARY

An integrally bladed disk includes a rotor disk and circumferentiallyspaced first and second blades. The rotor disk has a rim the peripheryof which forms a flow surface. The first and second blades extendintegrally outward from the rim. The rim defines a trench in the flowsurface between the first and second blades aft of a leading edge of therim. The trench extends axially forward and rearward of a leading edgeof the first blade.

A gas turbine engine having a stress relief feature includes an integralrotary body and a blade. The blade extends from a fillet in a peripheralrim. The peripheral rim forms a depression that extends into the fillet.

An integrally bladed disk includes a rotor disk and circumferentiallyspaced first and second blades. The rotor disk has a rim the peripheryof which forms a flow surface. The first and second blades areintegrally joined to the rim. Each blade includes a fillet along a basethereof between each blade and the rim. The rim defines a trench in theflow surface between the first and second blades that extends into atleast one of the fillets.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic sectional view of one embodiment of an aircraftturbofan engine.

FIG. 2A is a perspective view of a circumferential section of oneembodiment of an integrally bladed rotor disk having flow path trenchesin the perimeter thereof.

FIG. 2B is a radial sectional view of the integrally bladed rotor diskillustrated in FIG. 2A.

FIG. 2C is a top perspective view of the perimeter of the integrallybladed rotor disk illustrated in FIG. 2A.

FIG. 3A is a perspective view of a circumferential section of anotherembodiment of an integrally bladed rotor disk having flow path trenchesin the perimeter thereof.

FIG. 3B is a radial sectional view of the integrally bladed rotor diskillustrated in FIG. 3A.

FIG. 3C is a top perspective view of the perimeter of the integrallybladed rotor disk illustrated in FIG. 3A.

FIG. 4A is a perspective view of a circumferential section of yetanother embodiment of an integrally bladed rotor disk having flow pathtrenches in the perimeter thereof.

FIG. 4B is a radial sectional view of the integrally bladed rotor diskillustrated in FIG. 4A.

FIG. 4C is a top perspective view of the perimeter of the integrallybladed rotor disk illustrated in FIG. 4A.

DETAILED DESCRIPTION

FIG. 1 shows an axial cross-section of gas turbine engine 10 includingan engine axis 12, a fan 14, a compressor 16, a combustor 18, and aturbine 20. The fan 14 includes a casing that surrounds a rotor to whichthe blades of the fan are attached. An air stream 22 is pulled into thefront of engine 10 by the rotation of the fan 14 blades about the engineaxis 12. The fan 14 directs a portion of the air stream 22 into thecompressor 16. The air stream 22 is successively compressed throughstages of airfoils in the compressor 16 and is directed into thecombustor 18. The air stream 22 is mixed with fuel and ignited incombustor section 18 and is then directed into the turbine 20 where themixture is successively expanded through alternating stages of airfoilscomprising turbine rotor blades and stator vanes. A portion of the gasand fuel mixture leaving the combustor 18 acts to rotate turbine 20,which powers the fan 14 and the compressor 16. The remaining portion ofthe gas and fuel mixture passing through the turbine 20 exits the backof the engine 10 to provide thrust for the engine 10. Operating criteriasuch as the desired size, weight and thrust capacity of the gas turbineengine 10 and the acceptable stress limits due to centrifugal loads andthermal stresses experienced in some sections or stages of engine 10 cannecessitate that the rotor blades be integrally bladed to rotor disks.

FIGS. 2A-2C are views from various perspectives of a circumferentialportion of one embodiment of an integrally bladed disk 24A. Theintegrally bladed disk 24A is connected to the rotor in one or more ofthe various stages of the engine 10 (FIG. 1), including the fan 14,compressor 16, and/or turbine 20. The integrally bladed disk 24Aincludes a hub (not shown), a web 28, a rim 30, arms 32 and rotor bladesor airfoils 34 a and 34 b. The rim 30 includes a flow surface 36, aleading edge 38, a trailing edge 40, and trenches or dimples 42 a, 42 b,and 42 c. Each rotor blade 34 a and 34 b includes a leading edge 44, atrailing edge 46 and a fillet 48.

FIG. 2A shows the integrally bladed disk 24A and illustrates theradially innermost hub (not shown) (innermost relative to the engineaxis 12 shown in FIG. 1) which is connected to the rim 30 by the web 28.The arms 32 extend axially forward and aft (as defined by the flowdirection of a working fluid moving relative to engine axis 12 andpassing across the integrally bladed disk 24A) of the rim 30. The rotorblades 34 a and 34 b comprise a portion of a row of blades (not shown)and extend generally radially outwardly of the rim 30 in a unitary orsingle-piece manner. The flow surface 36 comprises the radial outerperiphery of the rim 30 adjacent the rotor blades 34 a and 34 b. Theflow surface 36 extends axially from the leading edge 38 to the trailingedge 40 as defined by the flow direction of a working fluid passingacross the flow surface 36. The flow surface 36 also extendscircumferentially between the rotor blades 34 a and 34 b. The trenches42 a, 42 b, and 42 c illustrated in FIGS. 2A-2C, are disposedcircumferentially adjacent each of the rotor blades in the row of rotorblades. The trench 42 b disposed circumferentially adjacent both therotor blades 34 a and 34 b. As will be discussed in further detailsubsequently, the geometry of the trenches and location of the trenchescan be modified in various embodiments of the integrally bladed disk toachieve a desired reduction in the hoop and principle stresses incurredon the integrally bladed disk during operation. The location andgeometry of the trenches can be optimized to design criteria usingcommercially available finite element analysis and computational fluiddynamics software such as software retailed by ANSYS, Inc. ofCanonsburg, Pa.

Each rotor blade 34 a and 34 b is integrally connected to the rim 30 andhas a conventional aerodynamic configuration with a generally concavepressure side and generally convex suction side for pressurizing theworking fluid during operation. The rotor blades 34 a and 34 b extendfrom the leading edge 44 to the trailing edge 46. The fillet 48aerodynamically transitions the root or base portion of each rotor blade34 a and 34 from the flow surface 36 of the rim 30. Each rotor blade 34a and 34 b defines, along with the blades disposed circumferentiallyadjacent to it (not shown), flow paths 50 a, 50 b and 50 c through whichthe working fluid is channeled during operation. The radially inwardpart of the flow paths 50 a, 50 b, and 50 c is defined by the flowsurface 36 and trenches 42 a, 42 b, and 42 c.

The geometry of the trenches 42 a, 42 b, and 42 c can vary depending oncriteria such as the application of the integrally bladed disk 24Awithin the engine 10 (FIG. 1) and the desired and acceptable stresstolerances. The trenches 42 a, 42 b, and 42 c shown in FIGS. 2A-2C, aredepressions in the rim 30 along the flow surface 36 where air (workingfluid) flowing along the integrally bladed disk 24A makes a transitionin flow direction. More generally, for the purpose of this application,“trench” or “depression” means a feature that causes a discontinuity inthe hoop direction of an integrally bladed disk. As shown in FIGS. 2Band 2C, the trenches 42 a, 42 b, and 42 c are disposed axially aft (asdefined by the flow direction of a working fluid moving relative to theengine axis 12 and passing across the integrally bladed disk 24A) of theleading edge 38 of the flow surface 36 but extend axially forward andrearward of the leading edges 44 of the rotor blades 34 a and 34 b. Inparticular, the deepest point of trenches 42 a, 42 b, 42 c are disposedto circumferentially align with a location of highest stressconcentration (a life limiting location) at a leading edge of the fillet48 of each rotor blade 34 a and 34 b.

In the embodiment illustrated in FIG. 2B the trench 42 a has a depth D₁of between about 0.005 inch (0.127 mm) and 0.060 inch (1.52 mm).Preferably, the depth D1 is between about 0.010 inch (0.254 mm) andabout 0.025 inch (0.635 mm). The radius R₁ of the trenches 42 a, 42 b,and 42 c can vary because, for example, the diameter of the head of themilling tool can vary. In the embodiment shown in FIG. 2B, trench 42 ahas a faired out radius R₁ (a radius that has a smooth transition from adeepest point of the trench 42 a to the flow surface 36 and/or theradius of fillet 48) into the flow path 50 a of about 0.10 inch (2.54mm) forward and aft of the trench 42 a. The distance the rotor blades 34a and 34 b are circumferentially spaced apart will vary as designcriteria dictates. The trenches 42 a, 42 b, and 42 c extendcircumferentially to adjacent the fillet 48 of each rotor blade 34 a and34 b. In other embodiments, the trenches 42 a, 42 b, and 42 c can bemilled to extend into the fillet 48 and/or can extend to the leadingedge 38 of the rim 30.

The trenches 42 a, 42 b, and 42 c cause the working fluid channeledthrough the flow paths 50 a, 50 b, and 50 c along the flow surface 36 tochange direction. This change in the direction of the flow reducesthermally and load induced principle stresses and the hoop stress on theintegrally bladed disk 24A. In particular, the trenches 42 a, 42 b, and42 c reduce stress concentrations at the rim 30 adjacent the leadingedges 44 and the pressure side of the rotor blades 34 a and 34 b. Byutilizing the trenches 42 a, 42 b, and 42 c as opposed to a conventionalintegrally bladed disk, a hoop stress reduction of about 10% to 25% anda reduction in principle stresses of about 5% to 15% for the integrallybladed disk 24A can be achieved. This stress reduction increases theoperation life cycle for the integrally bladed disk 24A by about 10×when compared to conventional integrally bladed disks without trenches42 a, 42 b, and 42 c.

FIGS. 3A-3C are views from various perspectives of a circumferentialportion of another embodiment of an integrally bladed disk 24B. Theintegrally bladed disk 24B illustrated in FIGS. 3A-3C has similarfeatures and operates in a manner similar to the integrally bladed disk24A shown in FIGS. 2A-2C. However, the integrally bladed disk 24Bincludes trenches 52 a, 52 b, and 52 c. The trenches 52 a, 52 b, and 52c are disposed circumferentially between each of the rotor blades in therow of rotor blades with the trench 52 b disposed between the rotorblades 34 a and 34 b. The trenches 52 a, 52 b, and 52 c are milled toextend adjacent each fillet 48 and extend axially forward and rearward(aft) of the leading edges 44 of the rotor blades 34 a and 34 b. Inother embodiments, the trenches 52 a, 52 b, and 52 c can extend into thefillets 48. In particular, the trenches 52 a, 52 b, and 52 c extendaxially to about the trailing edge 46 of the rotor blades 34 a and 34 b.The trenches 52 a, 52 b, and 52 c can all have a substantially identicaldepth D₂ of between about 0.005 inch (0.127 mm) and 0.060 inch (1.52 mm)or, in other embodiments, each trench 52 a, 52 b, and 52 c can have adepth D₂ that differs from the depth of the other trenches. The radiusR₂ of the trench 52 a and all the trenches can vary because, forexample, the diameter of the head of the milling tool can be varied.

FIGS. 4A-4C are views from various perspectives of a circumferentialportion of another embodiment of an integrally bladed disk 24C. Theintegrally bladed disk 24C illustrated in FIGS. 4A-4C has similarfeatures and operates in a manner similar to the integrally bladed disk24A shown in FIGS. 2A-2C. However, the integrally bladed disk 24Cincludes trenches 62 a, 62 b, 62 c, 62 d, 62 e, and 62 f. The trenches62 a, 62 b, 62 c, 62 d, 62 e, and 62 f are disposed circumferentiallyadjacent each of the rotor blades in the row of rotor blades with thetrenches 62 c and 62 d disposed between the rotor blades 34 a and 34 b.Although not illustrated extending into the fillet 48 of each rotorblade 34 a and 34 b, in some embodiments the trenches 62 a, 62 b, 62 c,62 d, 62 e, and 62 f can extend into the fillet 48. The trenches 62 a,62 c and 62 e are disposed adjacent the leading edges 44 of the rotorblades 34 a and 34 b and extend axially forward and rearward (aft) ofthe leading edges 44. As illustrated in FIGS. 4B and 4C, the deepestportion of trenches 62 a, 62 c and 62 e are disposed tocircumferentially align with a location of highest stress concentration(a life limiting location) at a leading edge of the fillet 48 of eachrotor blade 34 a and 34 b. The trenches 62 b, 62 d, and 62 f aredisposed circumferentially adjacent the rotor blades 34 a and 34 b withtrench 62 d disposed between rotor blades 34 a and 34 b. The axial andcircumferential location of the trenches 62 a, 62 b, 62 c, 62 d, 62 e,and 62 f relative the blades 34 a and 34 b and relative one another canbe varied or staggered to optimally reduce stresses and increase theservice cycle life of the integrally bladed disk 24C. Similarly, thegeometric shape or number of the trenches can be varied or staggeredrelative to one another to optimally reduce stresses and increase theservice cycle life of the integrally bladed disk. This optimization todesign criteria can be achieved by commercially available finite elementanalysis and computational fluid dynamics software. The trenches 62 aand 62 b illustrated in FIG. 4B have depths D₃ and D₄ of between about0.005 inch (0.127 mm) and 0.060 inch (1.52 mm). Depths D₃ and D₄ (anddepths of all the trenches 62 a, 62 b, 62 c, 62 d, 62 e, and 62 f) canbe substantially similar to one another or can differ from one another.The radii R₂ and R₃ of the trenches 62 a and 62 b (and all the trenches)on the integrally bladed disk 24C can vary because, for example, thediameter of the head of the milling tool can be varied.

Integrally bladed disks such as the ones illustrated in the FIGURES canbe manufactured by milling, forging, casting or other knownmanufacturing operations. If a milling process is used to manufacturethe integrally bladed disk, the trenches can be milled along with themilling of flow paths 50 a, 50 b and 50 c to save time and reduce oreliminate the need for additional processes to create the trenches.

Discussion of Possible Embodiments

The following are non-exclusive descriptions of possible embodiments ofthe present invention.

An integrally bladed disk includes a rotor disk and circumferentiallyspaced first and second blades. The rotor disk has a rim the peripheryof which forms a flow surface. The first and second blades extendintegrally outward from the rim. The rim defines a trench in the flowsurface between the first and second blades aft of a leading edge of therim. The trench extends axially forward and rearward of a leading edgeof the first blade.

The integrally bladed disk of the preceding paragraph can optionallyinclude, additionally and/or alternatively, any one or more of thefollowing features, configurations and/or additional components:

the trench extends axially to about a trailing edge of the first andsecond blades;

the trench has a depth of between about 0.005 inch (0.127 mm) and 0.060inch (1.52 mm);

a base of each of the first and second blades has a fillet;

a deepest point of the trench circumferentially aligns with a locationof highest stress concentration at a leading edge of the fillet;

the trench extends into at least one fillet;

the rim defines two or more axially spaced trenches, each of the two ormore trenches extends into the at least one fillet at different axiallyspaced locations; and

the blades comprise two of a row of blades and a plurality of axiallyspaced trenches are disposed between each blade in the row.

A gas turbine engine having a stress relief feature includes an integralrotary body and a blade. The blade extends from a fillet in a peripheralrim. The peripheral rim forms a depression that extends into the fillet.

The gas turbine engine of the preceding paragraph can optionallyinclude, additionally and/or alternatively, any one or more of thefollowing features, configurations and/or additional components:

the depression extends axially forward and rearward of a leading edge ofthe blade;

the depression extends axially to about a trailing edge of the blade;

the depression has a depth of between about 0.005 inch (0.127 mm) and0.060 inch (1.52 mm);

a deepest point of the depression circumferentially aligns with alocation of highest stress concentration at a leading edge of thefillet;

the blade is one of a row of blades and at least one depression isdisposed between each of the blades in the row; and

the blade is one of a row of blades and a plurality of depressions aredisposed between each of blades in the row.

An integrally bladed disk includes a rotor disk and circumferentiallyspaced first and second blades. The rotor disk has a rim the peripheryof which forms a flow surface. The first and second blades areintegrally joined to the rim. Each blade includes a fillet along a basethereof between each blade and the rim. The rim defines a trench in theflow surface between the first and second blades that extends into atleast one of the fillets.

The integrally bladed disk of the preceding paragraph can optionallyinclude, additionally and/or alternatively, any one or more of thefollowing features, configurations and/or additional components:

a deepest point of the trench circumferentially aligns with a locationof highest stress concentration at a leading edge of at leas one of thefillets;

the trench has a depth of between about 0.005 inch (0.127 mm) and 0.060inch (1.52 mm);

the trench extends axially forward and rearward of a leading edge of thefirst blade; and

the rim defines two or more axially spaced trenches, each trench extendsinto the at least one fillet at different axially spaced locations.

While the invention has been described with reference to an exemplaryembodiment(s), it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted forelements thereof without departing from the scope of the invention. Inaddition, many modifications may be made to adapt a particular situationor material to the teachings of the invention without departing from theessential scope thereof. Therefore, it is intended that the inventionnot be limited to the particular embodiment(s) disclosed, but that theinvention will include all embodiments falling within the scope of theappended claims.

1. An integrally bladed disk, comprising: a rotor disk having a rim theperiphery of which forms a flow surface; and circumferentially spacedfirst and second blades extending integrally outward from the rim,wherein the rim defines a trench in the flow surface between the firstand second blades aft of a leading edge of the rim, wherein the trenchextends axially forward and rearward of a leading edge of the firstblade.
 2. The integrally bladed disk of claim 1, wherein the trenchextends axially to about a trailing edge of the first and second blades.3. The integrally bladed disk of claim 1, wherein the trench has a depthof between about 0.005 inch (0.127 mm) and 0.060 inch (1.52 mm).
 4. Theintegrally bladed disk of claim 1, wherein a base of each of the firstand second blades has a fillet.
 5. The integrally bladed disk of claim4, wherein a deepest point of the trench circumferentially aligns with alocation of highest stress concentration at a leading edge of thefillet.
 6. The integrally bladed disk of claim 4, wherein the trenchextends into at least one fillet.
 7. The integrally bladed disk of claim6, wherein the rim defines two or more axially spaced trenches, each ofthe two or more trenches extends into the at least one fillet atdifferent axially spaced locations.
 8. The integrally bladed disk ofclaim 1, wherein the blades comprise two of a row of blades and aplurality of axially spaced trenches are disposed between each blade inthe row.
 9. A gas turbine engine having a stress relief feature, theengine comprising: an integral rotary body having a blade extending froma fillet in a peripheral rim, wherein the peripheral rim forms adepression that extends into the fillet.
 10. The gas turbine engine ofclaim 9, wherein the depression extends axially forward and rearward ofa leading edge of the blade.
 11. The gas turbine engine of claim 9,wherein the depression extends axially to about a trailing edge of theblade.
 12. The gas turbine engine of claim 9, wherein the depression hasa depth of between about 0.005 inch (0.127 mm) and 0.060 inch (1.52 mm).13. The gas turbine engine of claim 9, wherein a deepest point of thedepression circumferentially aligns with a location of highest stressconcentration at a leading edge of the fillet.
 14. The gas turbineengine of claim 9, wherein the blade is one of a row of blades and atleast one depression is disposed between each of the blades in the row.15. The gas turbine engine of claim 9, wherein the blade is one of a rowof blades and a plurality of depressions are disposed between each ofblades in the row.
 16. An integrally bladed disk, comprising: a rotordisk having a rim the periphery of which forms a flow surface; andcircumferentially spaced first and second blades integrally joined tothe rim, wherein each blade includes a fillet along a base thereofbetween each blade and the rim, and wherein the rim defines a trench inthe flow surface between the first and second blades that extends intoat least one of the fillets.
 17. The integrally bladed disk of claim 16,wherein a deepest point of the trench circumferentially aligns with alocation of highest stress concentration at a leading edge of at leasone of the fillets.
 18. The integrally bladed disk of claim 16, whereinthe trench has a depth of between about 0.005 inch (0.127 mm) and 0.060inch (1.52 mm).
 19. The integrally bladed disk of claim 16, wherein thetrench extends axially forward and rearward of a leading edge of thefirst blade.
 20. The integrally bladed disk of claim 16, wherein the rimdefines two or more axially spaced trenches, each trench extends intothe at least one fillet at different axially spaced locations.